CD150, also known as SLAM (Signaling Lymphocytic Activation Molecule), is a type I transmembrane glycoprotein belonging to the immunoglobulin superfamily and encoded by the SLAMF1 gene. It is primarily expressed on various hematopoietic cells, including T cells, B cells, natural killer cells, dendritic cells, monocytes, and macrophages. CD150 serves multiple functions: it acts as a co-stimulatory molecule in immune cell activation, a receptor for morbilliviruses such as measles virus, and a bacterial sensor on macrophages. The protein has several isoforms, including a transmembrane form (mCD150), a secreted form (sCD150), and a novel transmembrane form (nCD150) with an alternative cytoplasmic tail. CD150 mediates homophilic interactions and can transmit either activating or inhibitory signals depending on the cell type and context.